1. Field of the Invention
The present invention relates generally to a control system which controls the operation of both the engine and the transmission and more specifically to such a control system which includes a malfunction detection arrangement which enables the detection of inappropriate torque down control.
2. Description of the Prior Art
JU-A-61-108886 discloses a control arrangement of the type wherein, when the engagement of the friction elements is insufficient to transmit the amount of torque which is being produced by the engine, the ignition timing is adjusted in a manner to reduce the amount of torque being produced.
However, in systems wherein this measure is employed to reduce engine torque, in the case of a malfunction, the engine response to a given demand for engine power output (e.g. accelerator pedal depression) is such as to produce more torque than can be handled by the given friction element engagement to the degree that element slippage occurs.
Accordingly, when the engine torque reduction function is lost due to a control malfunction, it is necessary to inform the driver of the situation and to provide a fail-safe.
However, in the event that the engine throttle valve opening is small, even if the engine torque reduction control is lost, as the amount of torque which is being produced by the engine under such circumstances is very small the detection of a malfunction is rendered extremely difficult.